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Clingier? Silkier? It's All in the Catalyst, Says Chemist
Story posted July 28, 2006
When Professor of Chemistry Rick Broene shops for shampoo, he has all the advantages of his profession. He can scan the list of largely man-made ingredients and know exactly what he is using.
One chemical in particular often catches his attention: a derivative of a petroleum distillate called dodecyl sulfate.
It’s a product that shampoo manufacturers claim makes hair “silkier.” The same petroleum distillate puts the “cling” in Glad® Wrap. More importantly, says Broene, it has brought his research into a whole new area.
Broene, an organometallic chemist, has spent the past two years developing new catalysts that streamline the process of forming what are known chemically as alpha olefins - the precursors to hair silkeners or clingier plastics.
The synthetic molecules are formed through a common process known as polymerization, in which large molecules are formed by combining smaller molecules in a regular pattern. In this case, two six-carbon molecules combine to give one twelve-carbon molecule. The olefin (a carbon-carbon double bond) is in the first, or alpha, position.
“Previously,” notes Broene, “scientists were able to put the olefin in the middle, or elsewhere, but no one had been able to make it favor the end of the chain. This created a lot of waste. What I did was to develop a catalyst – a metal supported by various organic molecules – that would speed up the reaction and also cause better selectivity for the alpha olefin. The result is a better yield of alpha olefins with less waste.”
While the commercial potential of his discovery might be promising, Broene is actually more interested in the catalytic ingredients than he is the actual product they help to create.
The catalyst he ultimately used was cobalt, a metal found on the right side of the periodic table (late-transition metals). Until recently, much of Broene’s research has centered on metals that are found on the left side of the periodic table.
"Late-transition metals tend to be less oxygen-reactive and less water-reactive, so my students might have an easier time working with them than with the early-transition metals,” says Broene, who has involved over 40 undergraduate students in his work since coming to Bowdoin in 1993.
This summer, four Bowdoin student researchers are working in Broene’s lab – two of whom are concentrating on improving the alpha olefin catalyst.
“We’re trying to modify the catalyst to get better results than what we got in our first successful steps,” says Broene. “We know that bigger supporting molecules for this catalyst cause us to get less selectivity, so we’re trying to make the things that stabilize our catalyst be as small as possible.
“Hopefully we’ll find something. Or maybe we’ll find something new. That is what science is about: Being a careful enough observer to realize that if the reaction didn’t do what you wanted it to do, perhaps it did something more interesting.”
Broene’s findings on alpha olefins were published in the Journal of the American Chemical Society in 2005.
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